Ps. 90.11 (before the rhetorical question)

Who knows / the power of your anger
and your wrath / according to the fear do you. 

There are several things we need to note in these two questions. The first one is the fact that these are clearly rhetorical questions. No one knows the power of Yhwh’s anger. This sense of being utterly incapable of comprehending Yhwh is similar to the opening verses affirmation of Yhwh’s astonishing superiority, and priority, to every aspect of his creation. When the psalmist contemplates both of these aspects to Yhwh he is completely caught up short. What this signals here is important—that Yhwh’s wrath, his ‘moral displeasure’, is just as ‘deep’ as his creation-power. It extends into a realm that man is unable to enter because of its complete transcendence, its ‘always more’ than what could be grasped. Man can perceive Yhwh’s creation-power, and he can perceive Yhwh’s wrath; he cannot comprehend (or, encompass) either. The ‘superiority’ of Yhwh’s wrath, however, unlike creation, obtains its depth in tandem with man. What I mean is this: man is incapable of perceiving his own moral reality. Yhwh’s people has ‘hidden sins’. Yet, it is those hidden realities that ignite Yhwh’s wrath; it is those hidden sins that stand as ‘light’ to Yhwh. The people’s historical experience of ‘toil and trouble’ stands as an expression of this mystery and as a reality they are simultaneously aware that they have caused and that they are unable to rectify. 

We should see how much mystery pervades this psalm, the mystery of Yhwh and the mystery of man. Creation and history are the recipients and enactment of that mystery. Man’s life, as lived within that reality, is comic (in a tragic way). Which, is why, from that reality, there emerges this rhetorical question. It is as if the psalmist were saying to Yhwh, “We are aware our lives’ toil and trouble is our own doing, but we will never know ourselves as well as you. We can never overtake ourselves. Our sins will forever be before you, because you are forever before us.”